> > We've got a little Linux box based on P100 with a mono hercules monitor.
> > I've noticed that scrolling the screen can completly locks the machine
> > while scrolling is proceed. I was playing an MP3 and paging witin 'less'
> > produces strange sound output. If I scroll continously I can 'stop' mp3
> > playing for seconds as well. mpg123 ran with -20 and realtime priority ...
> > What's the matter ? It's not issued with eg a VGA card ...
>
> Easy: hercules can not do hw scroll, and it takes long time to repaint
> screen over ISA bus. Take a sun4 and see for how long you can stop
> _that_ with simple scrolling.
AFAIR, HGC has 32 kB of primary RAM the screen window may be located
within -- much like CGA, only mapped to ISA at different addresses. It
has also 32 kB of secondary RAM decoding of which has to be enabled
explicitly and which is used in HGC's graphics mode, usually.
In fact, almost all standard IBM PC video adapters have the ability to hw
scroll in the text mode. The only exception is the original MDA. I do
not know of any implementation bugs but all cards I tested were able to hw
scroll.
Linux does not make use of hw scrolling on HGC, though, and I am not
sure, why.
-- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
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